Boiler



FIG. 1 is a perspective view of the boiler, particularly showing theinventive design thereof;

FIG. 2 is a front view thereof;

FIG. 3 is a right side view thereof;

FIG. 4 is a top view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a bottom view thereof; and,

FIG. 7 is a back view thereof.

The broken-line disclosure in the views forms no part of the claimeddesign.

The ornamental design for a boiler, as shown and described.